Yes, Black Widow’s death makes no sense and let me tell you why?
After the snap of Thanos, half the living creatures in the universe were turned to dust, but the original 6 Avengers survived which includes Iron Man, Captain America, Thor, Hulk, Hawk-Eye, and Black Widow. All of the 6 were alive for a reason, but definitely not to die or I thought so.
In Avengers: Infinity War, when Thanos needed the soul stone, he blackmailed Gamora to reveal its location, because she is the only of whom he knew, knew about the whereabouts of the stone, he took her to Vormir where the soul was present. After reaching there, he understood that the only way to acquire the stone is to sacrifice something that he loved, he was sure he loved his daughter Gamora, he kills her and possesses soul stone.
Well, Nebula knows the whole story, when she was on Titan with the Guardians of the Galaxy and other Avengers, fighting Thanos. She could have said something about it when the whole team was going back in time to collect the stones in Endgame.
If you say Nebula didn’t know, I will disagree on that, because, when Nebula was captured by the Past Nebula and Gamora in the past, she tried convincing Gamora about what’s going to happen in Vormir with her and the soul stone, Nebula knew about the sacrifice right from the beginning of Avengers: Endgame, she cared not to say anything to Clint and Natasha Romanoff.
The movie had to be emotionally appealing I get that, Marvel Studios tried it that way, but Black Widow’s death is a blunder which MCU has to answer in the upcoming movies. She might have died unnecessarily.
There’s a movie coming, featuring Black Widow as the lead in the coming future of Marvel Cinematic Universe. The movie might take place before the events of Avengers: Infinity War. If we get lucky and somehow the Avengers try to bring her back from dead using the stones, the movie will take place after the events of Endgame. Till then let’s assume it to be a prequel.